In a rotor of an interior permanent magnet motor, the permanent magnets are buried in a magnetic core composed of laminated steel plates, for example. A stator is provided along the outer periphery or inner periphery of the rotor.
In the magnetic flux generated by the permanent magnets, the part passing only through the magnetic core without passing through the stator does not effectively contribute to the generation of torque. Accordingly, in order to reduce the magnetic flux passing only through the magnetic core, structures are proposed in which non-magnetic portions are provided at the ends of the permanent magnets, differed from the pole faces (For example, Patent Document 1). Also, proposed techniques include a technique in which the configuration of the non-magnetic portions is designed so as to reduce iron loss and copper loss (Patent Document 2), a technique in which a skew is obtained in a pseudo manner (Patent Document 3), and a technique in which odd harmonics are reduced (Patent Document 4).    Patent Document 1: Japanese Patent Application Laid-Open No. 11-98731 (1999)    Patent Document 2: Japanese Patent Application Laid-Open No. 2002-44888    Patent Document 3: Japanese Patent Application Laid-Open No. 2000-69695    Patent Document 4: International Publication 2005/004307